WPA && associating with unknown SSID

[Sam Leffler]

Pietro Cerutti wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> Sam Leffler wrote:
> | Matthias Apitz wrote:
> |> Hello,
> |>
> |> I'm using WPA to connect to my various Wifi AP's (office, home, 
> partner
> |> locations) and have them well configured in the wpa_supplicant.conf(5)
> |> file;
> |>
> |> from time to time at home I encounter that it is associating with an
> |> unknown AP of my neighbourhood:
> |>
> |>
> |> # ifconfig iwi0
> |> iwi0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu
> |> 1500
> |>         ether 00:13:ce:a1:e6:81
> |>         inet 192.168.2.3 netmask 0xffffff00 broadcast 192.168.2.255
> |>         media: IEEE 802.11 Wireless Ethernet autoselect (DS/11Mbps)
> |>         status: associated
> |>         ssid o2DSL_kJaR channel 1 (2412 Mhz 11g) bssid 
> 00:19:cb:86:b3:84
> |>         authmode OPEN privacy ON deftxkey 1 wepkey 1:40-bit bmiss 10
> |>         scanvalid 60 bgscan bgscanintvl 300 bgscanidle 250 
> roam:rssi11g 7
> |>         roam:rate11g 5 protmode CTS roaming MANUAL
> |> # ifconfig iwi0 list scan
> |> SSID            BSSID              CHAN RATE   S:N     INT CAPS
> |> o2DSL_kJaR      00:19:cb:86:b3:84    1   54M  19:0    100 EP
> |> xxxxxxxxxxxx    00:14:6c:44:aa:f6   11   54M  13:0    100 EP   WPA
> |>
> |> the network with SSID 'o2DSL_kJaR' is not im my
> |> /etc/wpa_supplicant.conf;
> |>
> |> how this is possible and how can I prevent this?
> |>
> | You must have a wildcard entry in your wpa_supplicant.conf file (i.e.
> | one w/o an ssid specified).
>
> Not necessarily. If you bring up a wlan interface and don't specify
> anything, it will automatically associate with the first open AP it 
> finds.
>
> I don't know if it's to be considered a feature or a bug. I've been
> worried by this sometimes, but honestly not enough to really care..
>
> Anyway, it happens...
>

He was talking about wpa_supplicant selecting an arbitrary AP.  If you 
have a device marked up then the system will handle ap selection+join 
but if wpa_supplicant is running then it marks the interface in "manual 
roaming mode" which stops that behaviour.

    Sam